Yay for overclocking!

http://www.youtube.com/watch?v=73pVTtsNa4g

What did you do to overclock the machine exactly? Are you switching in a different crystal?

Yes, I installed a 4-pin crystal oscillator. It outputs the same exact type of pulse the 68k normally accepts.

Pretty neat. You taught me something to day. Didn't know the sega ran sound off z80 and it use the other processor for graphics.

The Genny was loosely derived from Sega's 1985 "System 16" arcade board, and in arcades "68k for graphics and Z80 for sound" was nearly ubiquitous from the mid-80s through the early 90s. The SNES also has a second CPU for sound; their sound CPU and sound processor were designed for Nintendo by Sony's Ken Kutaragi, who later used beefed-up versions of that sound chip in the PlayStation and PS2.

The 68k also did the game engine too.

The system 16 uses a 10mhz CPU. This is why I chose a 10mhz overclock. So my genesis is essentially as fast as a true system 16. Though it still has a weaker graphics chip.

I may have to try this on my VA7 Genesis, since I'm planning to take it apart and do the 'crystal-clear audio' mod to it anyway.

I'm a little curious about the region mod, though... is there some particular reason you went with two switches, rather than a SP3T? Or is it just that you didn't have a SP3T laying around?

I went with the two switches because there is actually a 4th region, which entails JAP/50Hz. I don't think any games support it, but I didn't think about it until after I made the mod.